Background <p>Inguinal hernia surgery may trigger inflammation, and circadian variations in surgical timing could affect this response along with postoperative recovery. This study investigated how surgery timing influences inflammation, sleep quality, recovery, and pain in patients undergoing hernia repair.</p> Method <p>This prospective, randomized controlled trial was conducted at Ankara Bilkent City Hospital, with 70 patients undergoing elective unilateral inguinal hernia repair performed with a standardized open surgical technique. Participants, aged 18–70 and classified as ASA (American Society of Anesthesiologists) I–II, were randomized into two groups based on surgery timing: morning group (08:00–12:00, Group D) and evening group (18:00–22:00, Group N). Both groups followed standardized institutional fasting protocols, resulting in comparable fasting durations prior to surgery. All patients completed the Athens Insomnia Scale (AIS) preoperatively, and blood samples were collected to measure inflammatory markers including Neutrophil-to-Lymphocyte Ratio (NLR), Platelet-to-Lymphocyte Ratio (PLR), Mean Platelet Volume (MPV), Systemic Inflammation Index (SII), C-reactive Protein (CRP), fibrinogen, Erythrocyte sedimentation rate (ESR), procalcitonin (PCT), ferritin, and Interleukin-6 (IL-6). These parameters were reassessed 24&#xa0;h after surgery, and AIS was re-evaluated again on postoperative day 3.</p> Results <p>Sixty patients were included in the final analysis, with comparable demographics across groups. All inflammatory markers except MPV increased postoperatively in both groups; however, only IL-6 showed a significant between-group difference, with higher levels observed in the night group (<i>p</i> &lt; 0.001). Sleep quality was better in the day group on postoperative days 1 and 3 (<i>p</i> = 0.05; <i>p</i> = 0.019), and recovery scores were also higher (<i>p</i> = 0.001). Pain scores were similar except at the 8th hour, where the day group reported lower NRS (Numerical Rating Scale) scores (<i>p</i> = 0.032).</p> Conclusion <p> Daytime surgeries were associated with lower postoperative IL-6 levels and improved postoperative sleep quality and recovery. Although a statistically significant difference in pain scores was observed at the 8th postoperative hour, this finding was modest and did not affect overall analgesic consumption. These results suggest that surgical timing may influence certain short-term postoperative outcomes. These findings are specific to unilateral open inguinal hernia repair and may not be generalizable to more extensive, complex, or emergency surgical procedures.</p> Trial Registration <p>ClinicalTrials.gov (Registration No: NCT06345313, Date: 2024-03-27).</p>